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Introduction

For successful formation of new blood vessels, endothelial cells in an existing blood vessel must degrade the surrounding basement membrane. Upon activation by angiogenic stimuli, endothelial cells produce various matrix metalloproteinases (MMPs)–proteolytic enzymes that cleave the protein backbone of the basement membrane and surrounding extracellular matrix in order to facilitate cellular migration into the extracellular space.1

Assay Description

The matrix invasion assay is used to measure the ability of cells to degrade the basement membrane. Although it was originally developed to measure the invasive capability of tumor cells, it has been adapted for various cell types. This assay employs a modified Boyden chamber in which endothelial cells are placed in an upper compartment of a cell culture insert that contains a cell permeable membrane coated with a basement membrane extract. This extract occludes the pores of the membrane and prevents cell migration. Then a solution containing the test agent is placed below the cell permeable membrane. Following an incubation period (4–48 hours), the cells that have degraded the matrix and migrated through the membrane are stained and counted.

Variables affecting this assay that must be optimized by the investigator include cell type, cell seeding density, type and thickness of matrix barrier, incubation time, and type of angiogenic factor being tested. This assay has the advantage of being quantitative, flexible, and rapid. However, it can be difficult setting up the assay chamber. Commercially available cell culture inserts have alleviated this burden.